Shareholder Fees - FidelitySAIUSTreasuryBondIndexFund-PRO	Apr. 29, 2025 USD ($)
FidelitySAIUSTreasuryBondIndexFund-PRO \| Fidelity SAI U.S. Treasury Bond Index Fund
Shareholder Fees:
(fees paid directly from your investment)	none

Other Expenses

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form N-1A
-Section 3
-Subsection table
-Paragraph 1
-Subparagraph 10

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Namespace Prefix:	rr_
Data Type:	rr:NonNegativeMonetaryType
Balance Type:	na
Period Type:	duration